Mechanical Compliance: From Soft Robot Modeling Theory to FEM Computation

This chapter proposes a generic modeling method for soft robots. This method is based on the notion of mechanical compliance, which provides a compact description of the behavior of a deformableDeformable robot. In particular, the kinematicsKinematics of a soft manipulator arm can be derived from this notion. The chapter then shows how this complianceCompliance can be calculated from an analysis of the robot’s materials and mechanical structure. Starting from continuum mechanics, we describe how the equations can be integrated using the finite element methodFinite element method (FEM). This method is known to be computationally time-consuming, so the chapter briefly introduces the notion of model reduction by projection. Then, using a Lagrangian formulation, actuation, end-effectors, sensors and contacts are introduced which are essential for robot modeling and not often found in FEM formulations. In particular, models for fluidic, tendon-based and articulation-based actuatiors are detailed. Finally, this chapter describes how to obtain inverse models on soft robots and how to use them to invert kinematics, measure external forces without any force sensor or take contactsContact into account in the robot model-based controlNonlinear dynamic.